Krixix is the only in-game source of the ability Smelt Enchanted Elementium. He drops Goblin's Guide to Elementium. Pre-patch 3.0.8, it was obtainable by having a priestmind control him, then casting a spell that teaches the ability. After the patch, he drops a book which teaches the skill. Only one book drops and only one Miner can obtain and learn it. However, if you were in a raid, you can return to Blackwing Lair after a period of time and find that Master Elemental Shaper Krixix has respawned and is ready to drop it again.

Krixix requires a 30 minute soft reset to respawn again. In other words - if you are looking to farm him for elementium ore then no one should be in Blackwing Lair for 30 minutes straight.